1. Field of the Invention
The present invention relates generally to the field of chemical gas and liquid containment and delivery systems. More specifically, the present invention relates to an apparatus and process for safely delivering a hazardous fluid substance such as chlorine gas from a supply cylinder to a receiving structure or system, such as to a distribution cylinder or to a pool chlorine gas treatment system, with secondary containment and otherwise in accordance with government regulations. These regulations specifically include Toxic Gas Ordinance No. 23450, Chapter 17.78 of the San Jose Municipal Code, and the Uniform Fire Code, Article 20, Hazardous Materials.
The apparatus includes a high pressure containment vessel for receiving and safely enclosing a supply cylinder having a release valve and containing a hazardous fluid substance at a pressure above ambient. A high pressure flex line extends from the supply cylinder release valve to an automatic gas sensing valve assembly mounted in a vessel port in the vessel wall. The gas sensing valve assembly automatically shuts off the flow of gas through the vessel port when a gas leak is detected outside the containment vessel. Chlorine gas passes through the valve assembly and into a receiving structure or system, such as a gas manifold having coupling ports to which one or more distribution cylinders, also known as service cylinders, are removably connected. A back-up, manually operated valve is also provided in series with the automatic gas sensing valve assembly. The sensing valve assembly has a fail-safe-to-close design and the back-up valve is fitted with spring-returned, normal-closed or quick-turn lever handled Hastaloy.TM. "C" ball valves. The sensing and back-up valves both have reduced-orifice controllers.
To meet secondary containment requirements, the gas manifold is enclosed within an exhausted enclosure connected to a gas scrubbing unit. The scrubbing unit is substantially smaller than scrubbers typically used in the industry, because most of the gas is automatically sealed within the supply cylinder by the sensing valve assembly and within any distribution cylinders by reduced orifice flow controller on the manifold coupling ports. Should the supply cylinder leak, the gas it contains may be released into the scrubbing unit at a very low rate, and alternatively may be released instead into a gas cylinder rather than scrubbed and wasted.
The delivery process is inventively passive, so that dependence upon electric power for safe containment and flow is eliminated. The process includes the steps of placing a supply cylinder into a containment vessel; connecting the supply cylinder release valve to a tubing means extending through a fluid substance sensing valve assembly in the vessel wall. Optional additional steps include delivery of the fluid substance from the gas sensing valve assembly into a gas manifold; and delivering the gas from the manifold into a cooled distribution cylinder. Fluid substance contained within the supply vessel and gas manifold is maintained at ambient temperature so that gas pressure is minimized for safe retention. The distribution cylinder or other receiving structure or system is cooled below ambient to receive gas at low pressure. In this way the flow of gas results from the pressure differential between the supply cylinder and receiving structure rather than from the mechanical action of drive means, so that fluid substance containment and apparatus operation is passive, and high pressures are safely avoided.
2. Description of the Prior Art
There have long been gas delivery and transfer systems for delivering hazardous fluid substances from a supply cylinder, which is typically a one ton cylinder, into a receiving structure or system, such as a distribution cylinder, which is typically a fifteen or twenty pound cylinder. Recent government environmental and safety regulations have required that delivery or transfer take place within secondary containment. This has been accomplished in the chlorine industry in either of two ways.
One way has been to make the transfer in a room filled with massive and very costly scrubber equipment, so that if a leak develops, all gas in the supply cylinder can be very rapidly scrubbed from the air. This process makes it necessary to shut down operation in the room for one or more days and also results in the loss of all chlorine in the supply cylinder, both of these consequences being very expensive in addition to the cost of the scrubbing equipment. Should leakage take place during a power outage, particularly during a natural disaster, the scrubbing equipment would not function, so that the dangerous chlorine gas would escape into the neighborhood and into nearby ecosystems.
The other known way of transferring chlorine gas is with the use of what is known as a "coffin", which is essentially an ordinary sheet metal cabinet. The supply cylinder and distribution cylinder are both placed inside the coffin. The coffin has a release port opening into a powerful suction and scrubber assembly. In the event of supply cylinder leakage, the scrubber assembly must be activated immediately to rapidly draw away all of the escaping gas which includes the entire contents of the supply cylinder. The coffin would not contain the gas in the event that a power failure shut down the scrubber. Thus the problems of the scrubbing room are substantially presented by the coffin and scrubber containment system.
It is thus an object of the present invention to provide a hazardous fluid substance delivery system which provides the safe secondary containment required by law.
It is another object of the present invention to provide such a system which is compact and which requires minimal shutdown time in the event of a fluid substance leak.
It is another object of the present invention to provide such a system which safely retains any of the fluid substance leaking from the supply cylinder which has not reached the receiving structure or system, for gradual release into gas cylinders or into a scrubbing unit.
It is another object of the present invention to provide such a system which can release gaseous substances at a slow, controlled rate and thus requires only a small, low capacity and inexpensive scrubbing assembly.
It is still another object of the present invention to provide such a system which safely and secondarily contains the vast majority of leaking fluid substance in the event of power failure such as during a natural disaster.
It is still another object of the present invention to provide such a system which automatically stops the flow of fluid substance from the containment vessel with a valve operated by a fluid substance sensing mechanism.
It is finally an object of the present invention to provide such a system which delivers or transfers a fluid substance by passive, low pressure means and which is compact and economical to build and operate.